Development of a linear brushless DC motor drive with robust position control

The design and implementation of a linear brushless DC motor (LBDCM) drive with robust position control are presented. Hall-effect sensors and linear encoders are employed to obtain information of moving member position. A simple but practical zeroing approach is proposed to correct the phase errors of current commands due to the mechanical installation misalignment of Hall-effect sensors. Then a current-controlled PWM inverter is properly designed to yield excellent armature current tracking control characteristics. As to position control, the dynamic model of the LBDCM drive is first estimated from measurements. Then a two-degrees-of-freedom controller is quantitatively designed to meet the given position-control specifications. A robust controller is designed to reduce the control peformance degradation due to system parameter changes and the effect of cogging force. Simulated and measured results are provided to demonstrate the driving performance of the whole linear motor drive.